The present invention relates to a method and a device for measuring angles or angle changes on objects.
Measuring systems according to the reflection method, which are used for measuring camber and toe of motor vehicles, are known from Patent Specifications CH 454 477, CH 451 532, and DE 2759 556 C2. In this case, a measuring scale is imaged using a projector over the reflecting surface, which is subjected to the angle change, on a matte disk and/or on a matte disk having optoelectronic converters. The disadvantage in this method is the required fixed reference distance between measuring device and mirror in order to obtain a sharp image on the matte disk, which must be read manually and may not be automated easily. In addition, a special, complex, and costly receiver having the optoelectronic converters and special analysis electronics is necessary for automatic ascertainment of the measured values due to the relatively great enlargement of the image. Furthermore, the number and size (packing density) of the optoelectronic converters are limited, so that the resolution and measuring range are too low for most applications.
Furthermore, determining angles or angle changes in a contactless way with the aid of an autocollimation telescope, in which a suitable projected object (typically crosshairs) is evaluated after reflection on a reflecting surface subjected to the angle change with the aid of a beam splitter and an objective acting as the collimator and telescope, is generally known in principle. Corresponding embodiments are known in, among other things, DE 33 11 945 A1, DE 197 41 290 A1, and U.S. Pat. No. 5,513,000. Instead of crosshairs, a pin diaphragm is positioned as the object in DE 197 41 290 A1. A disadvantage in these arrangements is that with increasing measurement distance, i.e., as the distance becomes greater between mirror and autocollimator, the angle measurement range is reduced because of shadowing through screen effects. The problem is known and/or described in U.S. Pat. No. 5,513,000. The autocollimator contains two switchable light sources therein, which are laterally offset within the object plane and thus allow two small measuring ranges. The problem in this case is that continuous measurement within a large measuring range is not possible. Furthermore, a system having collimator and telescope at an acute angle, in which a punctual light source functions as the object generator, is known from U.S. Pat. No. 5,883,709. However, this system also functions for large angles up to 30° only at very small distances between test object and receiver system, since the lens opening of the receiver collimator also vignettes and also does not solve the problems described above.